Brussels / 3 & 4 February 2018


Class Data Sharing

Sharing Economy in the HotSpot VM

Class Data Sharing (CDS) is a feature that was introduced in Java 5 to improve startup performance and reduce the memory footprint of the JVM by sharing the metadata of system classes between virtual machines running on the same host. During the last years, this feature has been constantly improved. In OpenJDK 10 CDS will be extended by AppCDS which additionally allows the sharing of application classes between VM instances (see JEP 310: Application Class-Data Sharing [1]).

In this talk I will briefly introduce CDS and AppCDS. After demonstrating its various use cases, I will do a short deep-dive into the implementation details and challenges. Finally I will briefly describe how Strings and Symbols can be stored in the CDS archive and shared across VM as well since OpenJDK 9.

After the talk, the audience should have a better understand of the CDS/AppCDS feature and be able to decide whether it makes sense to use it for their own applications.



Photo of Volker Simonis Volker Simonis